1. Field of the Invention
The present invention relates generally to a flame detecting device of a gas turbine starter combustor in a pressurized fluidized bed combined cycle power system, and specifically to that having a structure which is able to prevent dirt due to combustion gas ash from sticking.
2. Description of the Prior Art
FIG. 4 is a schematic view of a prior art pressurized fluidized bed combined cycle power system. In FIG. 6, fuel of coal or the like is burned at a pressurized fluidized bed boiler 13 so that steam system pipings thereof are heated to generate steam for driving of a steam turbine (not shown) as well as a high temperature combustion gas thereof, of about 800.degree. C. for example, is supplied into a gas turbine 11 via a duct 18 and its exhaust gas is discharged outside.
Air from a compressor 12, which is driven by the gas turbine 11, is supplied into the pressurized fluidized bed boiler 13 as a combustion air via a compressor outlet valve 14. On the other hand, at a plant start where the pressurized fluidized bed boiler 13 is not in a sufficient operation yet, because the high temperature combustion gas is not supplied into the gas turbine 11 sufficiently yet via the duct 18, the compressor outlet valve 14 is switched so that the air from the compressor 12 is taken into a starter combustor 30 as the combustion air via a duct 19, thus the gas turbine 11 is started by the starter combustor 30.
When the pressurized fluidized bed boiler 13 is heated, the compressor outlet valve 14 is switched so that the air from the compressor 12 is stopped to flow into the starter combustor 30 and the gas turbine 11 is started by the high temperature combustion gas from the pressurized fluidized bed boiler 13 to come in an ordinary operation.
FIG. 7 is a detailed cross sectional view of the starter combustor 30 mentioned above. In FIG. 7, the high temperature combustion gas from the pressurized fluidized bed boiler 13 enters portion A and gas generated by combustion therein is supplied into the gas turbine 11 via portion B. Numeral 31 designates a pipe fitted to the combustor main unit. The pipe 31 comprises an inner cylinder 32 and there is disposed a fuel nozzle 33 close to one end of the inner cylinder 32. Light oil is supplied to the fuel nozzle 33 to be injected into the inner cylinder 32 for combustion in the combustor main unit.
A fitting pipe 36, having a flame detector 34 fixed to its one end, is inserted into the inner cylinder 32 from outside so as to connect to an interior of the inner cylinder 32 for detection of flames. Numeral 39 designates a combustion air inlet and the air flowing through the compressor outlet valve 14 is led into the combustor main unit for combustion via portion C.
FIG. 8 is a detailed cross sectional view of a flame detecting device including the flame detector 34 mentioned above. An adapter 35, having therein a through hole, has its one end fitted to the fitting pipe 36 and the flame detector 34 is fitted to the other end of the adapter 35. The fitting pipe 36 is fixed to the combustor main body and a pipe 38 is inserted in the fitting pipe 36 so as to connect at one end of the pipe 38 to the inner cylinder 32 and at the other end to the through hole of the adapter 35 and to the flame detector 34. Numeral 37 designates a glass plate provided on an end portion of the flame detector 34.
In the flame detector 34 fitted as mentioned above, there is incorporated a photoelectric element and state of flames is detected through an end portion 38a of the pipe 38 opening to the inner cylinder 32 such that ultraviolet rays generated by the flames are led to the photoelectric element and state of the flames is detected by the strength thereof.
In the pressurized fluidized bed combined cycle power system as described above, there is provided the starter combustor 30, which is operated at a plant start for starting the gas turbine 11. When the temperature of the pressurized fluidized bed boiler 13 rises, operation of the starter combustor 30 is stopped so that the gas turbine 11 is then driven by the high temperature gas from the boiler 13 for ordinary operation. In the gas turbine 11 of such pressurized fluidized bed combined cycle power system, fuel such as coal or the like is burned by the pressurized fluidized bed boiler 13 and the high temperature gas so generated is used as an operating fluid, hence, while the plant is in ordinary operation or while the pressurized fluidized bed boiler 13 is being cooled after the plant is stopped, coal ash contained in the operating fluid enters the flame detector 34 through the end portion 38a which is open to the inner cylinder 32 and sticks to a surface of the glass plate 37 resulting in a loss of the flame detector 34 function.